In recent years, demand for high-definition satellite images of outer space and Earth is increasing in various fields. Accordingly, there is demand for the development of an observation satellite installed with a telescope having a higher resolution than a conventional telescope. To improve the resolution of the telescope in this type of satellite, it is necessary to structure the telescope not only to have a large mirror, but also to be sufficiently rigid to hold the large mirror when launched into space, and to exhibit thermal dimensional stability.
When a temperature distribution occurs over the telescope structure in a space environment and the thermal dimensional stability is low, the telescope structure becomes distorted, leading to a reduction in the definition of the satellite images. It is therefore important to realize a telescope structure exhibiting low thermal expansion.
Here, as an example of the prior art, a honeycomb sandwich structure constituted by a honeycomb core made of carbon fiber reinforced plastic (CFRP) and a pair of CFRP skins that cover respective surfaces and respective sides of the honeycomb core has been proposed (see PTL 1, for example).
In the honeycomb sandwich structure described in PTL 1, the pair of skins are manufactured using skin CFRP in which skin carbon fibers are arranged quasi-isotropically, while the honeycomb core is manufactured using core CFRP in which core carbon fibers are arranged quasi-isotropically. Conventionally, a honeycomb core is manufactured using core CFRP in which core carbon fibers are arranged so as to intersect diagonally relative to a core height direction. In PTL 1, however, the core CFRP is formed such that the core carbon fibers are arranged not only in a parallel direction to the skin surface, but also in an orthogonal direction to the skin surface. With this configuration, a honeycomb sandwich structure that exhibits low thermal expansion and high rigidity even in an out-of-plane direction can be obtained.